Process and apparatus for precision folding of sheet metal

Abstract

A process is described which makes use of a folding press and a numerically controlled manipulator device provided with mechanical pincers; the sheet metal to be worked is gripped by the manipulator device and carried against an abutment shoulder disposed in front of the press; the alignment of the front edge of the sheet metal with the abutment shoulder is then tested by means of microswitches, and then the sheet metal is carried under the blade of the folding press utilizing, as reference co-ordinates for the movements of the manipulator, those of the abutment shoulder.

I claim: 
     
       1. A process for effecting automatic precision folding of metal sheets by means of a robotised numerically controlled manipulator device (6) and a folding press (3), characterised by the fact that it comprises the following steps: gripping of a metal sheet (2) by the said manipulator device (6);   positioning the said metal sheet (2), by means of the said manipulator device (6) against a fixed abutment shoulder (18) positioned in front of the said folding press (3) parallel to a blade (4) thereof and at a known and relatively small distance from the said blade (4);   checking the alignment of a front edge (21) of the said metal sheet (2) with the said abutment shoulder (18) and possible correction of the position of the said metal sheet (2) by means of actuation of the said manipulator device (6); and   displacement of the said metal sheet (2) into the folding position under the said blade (4) by means of the said manipulator device (6) utilising, as reference coordinates, the coordinates of the said abutment shoulder (18).   
     
     
       2. A process according to claim 1, characterised by the fact that the said checking phase is performed by activating a pair of end-of-stroke switches (19) mounted on the said abutment shoulder (18) at a separation substantially equal to or less than the width of the said metal sheet (2), and bringing the said front edge (21) of the metal sheet (2) against the said end-of-stroke switches (19). 
     
     
       3. A process according to claim 2 in which a manipulator device (6) is used comprising a pair of mechanical gripping pincers (12) for the said metal sheet (2), characterised by the fact that the said correction of the position of the said metal sheet (2) is obtained by opening the jaws (13) of the pincer (12) of the said manipulator device (6) which is located on the side of the first switch (19) of the said pair of end-of-stroke switches (19) with which the said front edge (21) of the metal sheet (2) comes into contact and continuing to move the said pincers (12) towards the said abutment shoulder (18) until both the said end-of-stroke switches (19) are pressed by the said front edge (21). 
     
     
       4. A process according to claim 2, in which a manipulator device (6) comprising a single mechanical gripping pincer (12) for the said metal sheet (2) is used, characterised by the fact that the said correction of the position of the said metal sheet (2) is obtained by making the said pincer (12) of the said manipulator device (6) turn towards the side where the first switch (19) of the said pair of end of stroke switches (19) with which the said front edge (21) of the metal sheet (2) comes into contact is located, and continuing to turn the said pincer (12) until both the said end-of-stroke switches (19) are pressed by the said front edge (21). 
     
     
       5. A system for effecting the automatic folding of metal sheets (2) comprising at least one folding press (3) and at least one robotised numerically controlled manipulator device (6) operable to grip and selectively position the said metal sheets (2) one at a time in a plurality of predetermined positions in which the said metal sheets are to be worked by the said folding press (3), characterised by the fact that is includes an abutment device (15) disposed frontally in advance of the said folding press (3) and connected to a central control unit (7) of the said manipulator device (6), the said abutment device (15) including at least one abutment shoulder (18) disposed parallel to a blade (4) of the said folding press (3), at a predetermined relatively small distance therefrom, and a plurality of pairs of end-of-stroke switches 19 carried by the said shoulder (18) and selectively activatable by the said central control unit (7), the said switches of said pairs (19) being disposed at different separations from one another. 
     
     
       6. A system according to claim 5, characterised by the fact that the said abutment device (15) further includes a reference bracket (20) for a front edge (21) of the said metal sheets (2), disposed perpendicularly projecting in front of the said abutment shoulder (18), and an attachment element (22) fixed to the front of the said folding press (3) immediately above the said blade (4) and rigidly carrying the said abutment shoulder (18) and the said reference bracket (20), the said attachment element (22) being projectingly disposed with respect to a frontal surface (23) of the said folding press (3) in such a way as to maintain the said abutment shoulder (18) at a predetermined distance from the said surface (23) such as to allow the free displacement of the said metal sheet (2) during folding. 
     
     
       7. A system according to claim 6, characterised by the fact the said end-of-stroke switches (19) are disposed on the said abutment shoulder (18) or adjacent one another and at the same height, and by the fact that the said abutment device (15) includes two fixed abutment shoulders (18) provided with the said end-of-stroke switches (19) disposed aligned with one another respectively above and below the said reference bracket (20). 
     
     
       8. A system according to claim 5, characterised by the fact the said robotised manipulator device (6) includes a pair of mechanical pincers (12) having separately controllable counterposed jaws (13). 
     
     
       9. A system according to claim 5, characterised by the fact that the said robotised manipulator device (6) includes a single mechanical pincer (12) capable of rotating parallel to the plane in which it lies. 
     
     
       10. A system according to claim 6, characterised by the fact that the said abutment device (15) includes a plurality of optical sensors (26) disposed to the said central control unit (7).